Optical devices or elements such as lenses, mirrors, wave plates, filters, volume Bragg gratings, prisms and the like are often mounted to an optical system, and particularly an experimental optical system, with an adjustable optical mount. An example of an optical system may include an optical bench or base having multiple optical devices and components mounted to the base with an orientation so as to provide an optical path which directs a light beam from one optical device to the next. Beams from lasers or other light sources are generally used for such applications. For such arrangements, an adjustable optical mount provides a mechanism to securely fasten an optical element to the optical bench or other component of the optical system and still allow for some adjustment of the orientation of the optical element.
Existing adjustable optical mounts may include embodiments having a first plate configured to have an optical element secured thereto. A second plate is disposed adjacent the first plate and includes three contact points extending from the second plate to the first plate. One or more of the contact points may be disposed on the end of an adjustment shaft, such as an adjustment screw, which is threaded to the second plate. The contact points may also be disposed in a detent on the first plate which allows rotation of the contact point relative to the first plate, but prevents the contact point from sliding or being transversely displaced along the first plate. One or more retractive members, such as springs or magnets, are fastened between the first and second plates so as to force the plates to be drawn together with the restorative force of the spring, springs, magnet or magnets. The attractive force generated by the retractive members between the plates is resisted by the three contact points against the respective detents of the first plate. In such an arrangement, rotation of an adjustment screw or shaft moves the adjustment screw relative to the second plate in order to adjust the separation between the plates at the adjustment screw position and thus the relative orientation of the first plate to the second plate.
In some cases, a piezoelectric type actuator may be used to rotate the adjustment screws. A reciprocating motion of abutting jaw elements against the threaded shaft of the adjustable optical mount in a first direction may be converted to a simple rotary motion of the threaded shaft when the reciprocating motion is slow enough such that the coefficient of friction between the threaded shaft and the abutting jaws transmits the motion of the jaws to the threaded shaft. The rotational motion of the threaded shaft results in a translational motion of the threaded shaft and respective movement of the first plate and any element such as an optical element secured thereto. The reciprocating motion of the abutting jaw elements against the threaded shaft in a second direction may be relatively fast such that the inertia of the threaded shaft prevents it from engaging with the reciprocating motion of the abutting jaw elements thereby resulting in the preservation of the position of the threaded shaft. In some instances, the restoring force which each jaw applies to the threaded shaft may be provided by a separate preload mechanism such as a clamp spring which may be coupled to each jaw element.
Variations in the restoring force between the threaded shaft and abutting jaws as applied by the clamp spring can result in variations in the static and dynamic torque measured by rotating the threaded shaft with a torque measurement device. This may negatively affect the performance of the mount. Variations in the restoring force applied to the abutting jaws by the clamp spring may be caused by the deformation of the clamp spring during assembly, variations in manufacturing, processing or materials of the clamp spring or the like. What has been needed is a preload mechanism which supplies a consistent restoring force between contact surfaces of the abutting jaws and the threaded shaft.